Rheoscopic fluids have been demonstrated in the past. These fluids generally comprise suspensions of microscopic crystalline platelets in a carrier liquid. They have been used to elucidate flow patterns in mechanical and chemical equipment, such as reactors, chemical processing equipment and heat exchangers to demonstrate laminar and turbulent flow patterns and to identify dead spaces (low flow areas) which can create processing or heat transfer problems during use of such equipment. One example of materials has also been used as a media in artistic display pieces. A common material for these purposes, referred to as Kalliroscopic fluids, is a water based composition which contains a suspension of about 1 to 5% of a non-soluble plate-like polymeric material (P. Matisse and M. Gorman, Phys. Fluids, 27, p 759 (1984)
U.S. Pat. No. 5,788,506 refers to the use of another example of such a material, identified as titanium oxide coated mica particles manufactured by Mearlin Corporation under the trade name Mearlin Hi-Lite Gold 9220C. The appearance of these particles, when added to a flowing stream of liquid, changes as light is reflected from particles which have a different orientation when the flowing liquid is observed.
Other examples of materials which can be used to demonstrate flow patterns are aluminum particles, and colloidal suspensions of vanadium pentoxide, milling yellow dye, imogolite [which is a natural hydrated aluminum silicate found in the clays of certain ash from Japanese volcanoes], gibbsite [which comprises hexagonal platelets of Al(OH)3], bentonite [Nax(Al2−xMgx)(Si4O10)(OH)2], LoniteB [Na2Ca)x/2(LixMg3−x)(Si4O10)], boehmite (γ-AlOOH) and akaganeite [βFeOOH].
U.S. Pat. Nos. 4,655,842, 4,780,147 and 4,801,403 describe the preparation of stable vermiculite dispersion. These dispersions are then used to prepare a broad range of films and coatings for industrial applications such as non-burning paper, flame barriers, fireproofing coatings on combustible materials, thermal and electrical insulation, and gaskets. Materials covered by the '842 and '147 patent are marketed by Grace Construction Products as MICROLITE Vermiculite Dispersions, a stable vermiculite dispersion in water. Goldberg describes use of such dispersions in the fabrication of water proof coatings for sports equipment (Goldberg, H. A., “Elastomeric Barrier Coatings for Sporting Goods” Rubber World, 226, no. 5, p 15-20, 37, August 2002) and shows a jar of a 0.02% MICROLITE viewed through crossed polarizers as an opaque solution with some bright areas to demonstrate the oriented nature of the vermiculite. While at least one of these suspensions has been described as “stable”, the stability of these suspensions in an unstirred state is for a matter of minutes or a few hours and not longer periods of time.